Phosphorus compounds containing stable halogen

ABSTRACT

NEW COMPOUNDS HAVE THE FORMULA:   R-O-P(=O)(-O-R&#39;&#39;)-(O)N-CH2-C(-CH2-R&#34;)3   WHEREIN N IS ZERO OR ONE; R IS LOWER ALKYL, PHENYL OR ALKYLATED PHENYL HAVING ONE TO THREE LOWER ALKYL SUBSTITUTENTS, R&#39;&#39; IS R OR   -CH2-C(-CH2-R&#34;)3   AND AT LEAST ONE R&#34; IS BR OR CL AND EACH REMAINING R&#34; IS OH, BR, OR CL. THESE COMPOUNDS ARE USEFUL FIRE-RETARDANT ADDITIVES IN PLASTIC, TEXTILE, AND OTHER NORMALLY FLAMMABLE MATERIALS. THEY ARE PARTICULARLY RESISTANT TO THE PRODUCTION OF HYDROGEN HALIDES AT ELEVATED TEMPERATURES.

3,830,886 ed Aug. 20, 1974 ME PHIS X 3 Elsifiilsfihlh v United St:

PHOSPHORUS COMPOUNDS CONTAINING STABLE HALOGEN Ralph A. Davis, Midland, and Ronald G. 'h'gner, North Bradley, Mich., assignors to The Dow Chemical Company, Midland, Mich.

No Drawing. Continuation-impart of abandoned application Ser. No. 736,557, June 13, 1968. This application Feb. 8, 1971, Ser. No. 113,046

Int. Cl. C07f 9/08, 9/38; C09]: 3/28 US. Cl. 260-953 9 Claims ABSTRACT OF THE DISCLOSURE New compounds have the formula:

11-0 0 CHiR" JE (O); CHQ-''-CHTR" rv-o inn" wherein n is zero or one; R is lower alkyl, phenyl or alkylated phenyl having one to three lower alkyl substitutents, R is R or GHQR -oH,-=h-cHiR";

Hi3" and at least one R" is Br or Cl and each remaining R" is These new compounds have unusual resistance to thermal and hydrolytic decomposition and are therefore su perior fire-retardant additives for wood, textiles, plastics, and the like.

DETAILED DESCRIPTION the mixture at reaction temperatures generally from 30 OH, Br, or Cl. These compounds are useful firegretardant' \Wadditives in plastics, textiles, and other normally flammable materials. They are particularly resistant to the production of hydrogen halides at elevated temperatures.

CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part of our copending application Ser. No. 736,557, filed June 13, 1968, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to novel chemical compounds useful as fire-retardant additives for combustible materials.

The use of fire-retardants containing both bromine or chlorine and phosphorus is well known in the art for use with normally flammable materials such as wood, cloth, and polymers such as polyesters and polyurethanes as described, for example, in US. Pats. 2,725,311; 2,803,- 562; 3,132,169; 3,157,613; and 3,192,242. However, the above and other prior fire-retardants sulfer from a number of disadvantages such as their tendency to produce hydrogen halides such as HBr when heated. This hydrogen halide tends to degrade wood fibers and polymers causing an undesirable loss in strength and darkening in color.

SUMMARY OF THE INVENTION According to the present invention, there are provided novel compounds of Formula I:

wherein n is zero or one; R is lower alkyl, or phenyl having up to three lower alkyl substituents, lower alkyl being defined as of 1-6 carbon atoms; R is R or CHiR" CHg- CHIR;

HQRII and at least one R" is Br or Cl and each remaining R" is OH, Br, or Cl. Br is the preferred halogen.

to C. for a period of from 1 to 20 hours.

The phosphorus-containing esters suitable for use in the present invention are the mono-, di-, and preferably trihydrocarbyl phosphates and phosphites where hydrocarbyl is phenyl having up to three lower alkyl substituents or lower alkyl where lower alkyl is defined as of 1-6 carbon atoms. Examples of suitable phosphorus-containing esters include, among others, ethyl phosphate, diethyl phosphate, triisopropyl phosphate, trihexyl phosphate, diphenyl ethyl phosphate, triphenyl phosphate, tritolyl phospate, tri-p-secbutyl phosphate, methyl phosphite, trlethyl phosphite, diisgibutyl phosphite, triphenyl phosphite, and trixylyl phosp te.

The halogenated alcohols suitable for use in the present invention are those of Formula 11:

(ll) OH R" HOOH ===-CH R" the alcohol, there is obtained predominantly the reaction of a halogen atom in the alcohol molecule and the resulting ester is largely that wherein the radical derived from the starting alcohol contains one less halogen atom while the main byproduct is an organic halide. On the other hand, when the phosphorus ester is a phosphite, the re action byproduct is largely an alcohol rather than the halide expected from a normal Arbusov reaction and the ester product is for the most part the alkanephosphonate wherein the substituted alkane group contains the same number of halogen atoms as the halogenated alcohol reactant.

Because of the above-described reaction peculiarities, the trihaloneopentyl phosphates are best prepared by another method. A convenient known synthesis whereby such trihalogenated esters are obtained comprises the re action of the trihalo alcohol of Formula II with a partially esterified phosphorus oxychloride of the formula (RO) POCl,, wherein m is one or two, p is two or one (m+p=3) and R is as defined above. The reaction is usually carried out in a neutral solvent such as diethyl ether at about or slightly above normal room temperature and preferably in the presence of an acid acceptor such as pyridine.

A wide variety of normally flammable materials can be rendered flame-retardant by treating them with the compounds of the present invention. Thus, such normal flammable materials such as wood and polymers such as polyurethanes and polyesters can be treated by applyirg a solvent solution of these compounds or, in polymer compositions, by incorporating the fire-retardant compound itself in the polymer by conventional means, either as such or in combination with other additives. Alternatively, wherein the compounds of the present invention contain one or more hydroxyl groups, these compounds can be chemically incorporated into a polyester by admixing the polyester with the polyol before reacting it with the polycarboxylic acid to form the polyester. Alternatively, these compounds can be introduced into polyurethanes by employing the hydroxyl group-containing compound as a portion of the polyol to be reacted with the polyisocyanate. As previously stated, these compounds have a high resistance to the production of hydrogen halides such as HBr Which can be demonstrated by mixing these compounds with an alkali metal hydroxide such as sodium hydroxide and testing for the presence of alkali metal halides such as sodium bromide.

The present halogenated phosphates and phosphonates have been found to be particularly effective fire-retardant additives for use in polyester resins. Polymers thus advantageously compounded with these additives comprise any of the commonly known polyesters of dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, tetrahydrophthalic acid, and especially terephthalic acid with aliphatic polyols or ether alcohols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, glycerol, pentaerythritol, diethylene glycol, dipropylene glycol, tricthylene glycol, or mixtures of any two or more of such polyols. In such polyesters, the halogenated phosphorus esters of this invention are found to provide a substantially higher degree of resistance to burning than structurally similar compounds when used in proportions such that the halogen content of the respective compositions is the same. The present compounds are also convenient to use in that they are ordinarily obtained as viscous liquids or low melting glassy solids which are easily compounded into resinous compositions to obtain uniform products.

The quantity of halogenated phosphate or phosphonate to be used in wood, wood products, cellulosic fibers, or various kinds of polymer resins as described above is not critical since any significant quantity will provide some added resistance to burning. In wood and other cellulosic materials, enough additive may be employed to give a total halogen content of the treated material of from about two to fifty percent or more. In resinous cornpositions such as polyesters someyhat smaller proportions are ordinarily used to minimize loss of useful properties in the plastic product. In such compositions, the halogenated additives may be used in proportions to provide a halogen content in the finished material of about one to about ten percent, depending upon the end use of the material and the degree of protection desired.

The invention is further illustrated by the following examples in which all parts and percentages are by weight unless otherwise indicated. These non-limiting examples are illustrative of certain embodiments and are designed to teach those skilled in the art how to practice the invention and to represent the best mode contemplated for carrying out the invention. In these examples, IR means infrared and NMR means nuclear magnetic resonance.

EXAMPLE I This example illustrates the preparation of diethyl (2, 2 bis(bromomethyl) 3 hydroxypropyl)phosphonate.

One hundred fifty-seven grams (0.6 moles) of 2,2-bis (bromomethyl) 1,3 propanediol and 100 ml. of toluene were charged to a 500 ml. 3-neck flask equipped with a stirrer, thermometer, addition funnel, and a A x Vigreux column equipped with a distillation head. The mixture was heated to 90 C. with stirring and 0.6 moles (100 g.) of triethyl phosphite added slowly over a period of 6 hours. A light fraction was distilled off at 60 to 75 C. The temperature was then raised to 110 to 126 C). for 5 hours and a second light fraction distilled at '75 to 107 C. A total of 89 g. of low boiling material was removed in this way. The balance of the light fraction and the solvent (toluene) was removed by heating the residue in a rotary evaporator to C. at 1 mm. Hg absolute pressure.

Analysis of this lower boiling material showed 0.8 g. moles of CH CH OH and 0.1 mole of CH CH Br plus toluene, and traces of unreacted triethyl phosphite. The light yellow, clear product recovered (l76 g.) was analyzed and found to contain 44.0% Br and 9.25% P corresponding to diethyl (2,2-bis(bromomethyl)-3-hydroxypropyl)phosphonate of Formula III:

which contains 41.9% Br and 8.1% P. NMR analysis indicated that the product contained about 85% of the compound of Formula III with some of the unreacted 2,2-bis(bromomethyl)-l,3-propanediol. IR analysis supported the phosphonate structure.

EXAMPLE II This example illustrates the preparation of diethyl (3- bromo 2,2 bis(bromomethyl)propyl)phosphonate.

One hundred sixty-two grams (0.5 g. mole) of white 3-bromo-2,2-bis(bromomethyl)-1-propanol and 50 ml. of toluene were charged to a 500 ml. 3-neck flask equipped as in Example I. The fiask and its contents were heated to C. and 83 grams (0.5 mole) of triethyl phosphite was added slowly and the low boiling reaction products distilled off as in Example I. The reaction time was 5 hours at 107 to 118 C. plus 6 hours at 120 C. Bromine analysis and the amount of recovered ethyl alcohol indicated that the product was a mixture of about 68% to 78% diethyl (3-bromo-2,2-bis(bromomethyl) propyl)phosphonate of Formula IV:

( 0 Omar (CHI-onto)Qlom(h-cnmr other and 20% to 30% of the compound of Formula [I]. NMR and IR analysis supported the phosphonate structure. IR showed the presence of some alcohol groups.

EXAMPLE III A quantity of 2,2-bis(bromomethyl)-l,3-propanediol, 131 grams (0.5 g. mole), and 100 ml. of toluene were charged to a 500 ml. 3-neck fiask equipped as in Example I. The mixture was heated to 104 C., and 91 grams (0.5 mole) of triethyl phosphate was added slowly with stirring. The reaction time was 3 hours at 104 to 120 C. plus 3 hours at 124 to 127; 2 hours at 12 to 152; and 4% hours at 174 to 177.'Ethyl bromide (0.52 mole) and a small amount of ethyl alcohol and toluene distilled from the reaction. The balance of the solvent was removed at 100 C. and 1.0 mm. Hg absolute pressure in a rotary evaporator.

One hundred thirty-six grams of dark amber, viscousl liquid were recovered. Chemical analysis of this material gave 22.6% Br and 10.4% P. This corresponds quite closely to the analysis for 3-bromo-2,2-bis(hydroxymethyl) propyl diethyl phosphate of Formula f:

.xI'IQOII containing 23.9% Br and 9.25% P. NMR analysis confirms the phosphate structure.

One-half gram-mole, 162 g. of 3-bromo-2,2-bis(brornomethyl)-1-propanol, and 50 ml. of toluene were charged to the flask of Example I. The mixture was heated to 110 C. and 0.5 mole, 91 g., of triethyl phosphate was added slowly with stirring. The mixture was heated to 100 to 168 C. for 4 hours and 168 to 199 for an additional 4 hours. Ethyl bromide, a small amount of ethyl alcohol, and most of the toluene were distilled off to leave the product. The product was stripped in a rotary evaporator at 100 C. at 1.0 mm. Hg absolute and 181 g. of a'=viscous amber liquid recovered. Chemical analysis of this product gave 41.1% Br and 8.2% P.'This plus the loss of ethyl bromide indicated that the product was essentially 2,2 bis(bromomethyl)-3-hydroxypropyl diethyl phosphate of Formula VI; 1

which contains 40.2% Br and 7.8% P. NMR analysis confirmed the phosphate structure. w

EXAMPLE V In the same manner as Example IV, 233 g., 0.72 mole, of (OH BrhCCH OH and 66 g., 0.36 mole, of triethyl phosphate were reacted. A dark amber, very viscous liquid (171 g.) was recovered plus 0.62 mole of ethyl bromide. The main product was bis(2,2-bis(bromomethyl)-3-hydroxypropyl) ethyl phosphate of Formula VII:

EXAMPLE v1 Two grams of film: chloride were added to a mixture of 266 g. of 3-bromo-2,2,-bis(bromomethyl)-'1-propanol,'

204 g. of crude isopropylphenol, and 200 ml. of toluene in a reaction flask. The crude isopropylphenol was an alkylation reaction product containing about 31% by weight phenol, 43% isopropylphenol (about 1.7/1 ortho/para), 21% diisopropylphenol (largely the 2,4- isomer), and 3% triisopropylphenol. The mixture was heated to 84 C. and 115 g. of POCl was added over a period of 4.75 hours, the heat of reaction raising the temperature of the mixture to 128 C. at the end of the addition. An additional two grams of zinc chloride were addedf'and the mixture was stirred at about 130 C. for another fifteen hours.

The reaction mixture was Washed with dilute ammonium hydroxide and dried with CaCl Toluene was evaporated off under 5 mm. Hg vacuum at 80-90 C. in a rotary evaporator to leave as the residue 460 g. of a light amber, extremely viscous liquid which slowly solidified on standing for several days. IR and elemental analysis together indicated that the product was largely a mixture of about two parts of the bis(isopropylphenyl) 3-bromo-2,2-bis(bromomethyl)propyl phosphate and one part of the isopropylphenyl"b-is(3-bromo-2,2-bis(brom0- methyl)propyl) phosphate wherein mono, di, and triisopropylphenyl groups were present in the proportions and orientations substantially as in the starting crude isopropylphenol. The bis(isopropylphenyl) ester has the formula H other o -1 o-oHi-o-orm3r. OH crnnr or. a

6 EXAMPLE VII The general procedure of Example VI was repeated using the same reactants in the same quantities except that the POCl was replaced by 103 g. of PCl Vacuum evaporation of the toluene solvent left as the reaction product 450 g. of a light colored, very viscous liquid. Some solid material formed on standing for several days. Infrared and elemental analysis showed that the product was a mixture of phosphonate with some unconverted phosphite. The phosphonate was a mixture of about 2.6 parts by weight of bis(isopropylphenyl) 3-bromo-2,2 bis(bromomethyl)propylphosphonate to one part of iso propylphenyl 3 bromo 2,2 bis(bromomethyl)propyl 3-bromo 2,2 bis(bromomethyl)propylphosphonate, the isomer distribution in the isopropylphenyl groups being substantially that in the starting isopropylphenol. The principal product, the bis(isopropylphenyl) ester has the formula EXAMPLE VIII Essentially as described in Example VI, a mixture of 266 g. of 3-bromo-2,2-bis(bromomethyl)-l-propanol and 225 g. of crude p-sec-butylphenol was reacted with 115 g. of. POCl in the presence of zinc chloride. The reaction product remaining after vacuum distillation of the toluene solvent was a light amber, extremely viscous material which was found by analysis as before to be largely bis(sec-butylphenyl) 3-bromo -2,2 bis (bromomethyl propyl phosphate with a small amount of the corresponding mono-sec-butylphenyl ester. The isomer distribution in the sec-butylphenyl groups corresponded essentially to that of the starting sec-butylphenol which was about mono-sec-butylphenol with minor amounts of phenol and di-secbutylphenol present. The sec-butylphenol contained about 8 parts of para isomer to one part of meta and 0.5 part of ortho-sec-butylphenol, This isomer distribuetion was reflected in the phosphate product. The bis (sec-butylphenyl) ester has the formula CHgBr EXAMPLE IX Using the method of Example VI, a mixture of ethyl alcohol and 3-bromo-2,2-bis(bromomethyl)-1-propanol in about 2:1.1 molar ratio was reacted with POCl to make the corresponding mixed phosphate. The product was a light amber viscous liquid which slowly solidified. Elemental analysis indicated that it was a mixture 01. about three parts diethyl 3-bromo-2,2-bis(bromomethyl)propyl phosphate and one part ethyl bis(3-bromo-2,2- bis(bromomethyl)propyl) phosphate.

EXAMPLE X By the procedure of Example VI, a 2: 1.1 molar mixture of phenol and 3-bromo-2,2-bis(bromomethyl)-1-propanol was reacted with POCl to make the mixed phosphate, an olT-white solid of relatively low melting point. Ele mental analysis showed the product to be a mixture of about 72 percent diphenyl 3-bromo-2,2-bis(bromomethyl)propyl phosphate and 28 percent of the corresponding monophenyl compound.

EXAMPLE XI Following the procedure of Example VII, a mixture of 188 g. of phenol and 390 g. of 3-bromo-2,2-bis(bromomethyl)-1-propanol was reacted in toluene with 137 g.

of PCl in the presence of zinc chloride. The reaction product after removal of toluene was a cloudy, nearly colorless, viscous material, weight=542 g. The product partially solidified on long standing to a glassy solid. It was analyzed as in the foregoing examples and found to be mostly diphenyl 3-bromo-2,2-bis(bromomethyl)propylphosphonate with some of the corresponding phosphite. The phosphonate has the formula EXAMPLE XII This example illustrates the flame retardancy of cloth and wood treated with the products of Examples I, II, and IV according to tests adapted from ASTM test 0626-- 411 (issued 1941) for cloth, and Department of Commerce Class F fire test CS42-49 for wood.

A 40% solution in CH Cl of each of the compounds listed in Column 2 of the following table was prepared for treating materials. 2 /2 x 10" strips of cotton muslin and viscose rayon were treated by wetting each strip with one of the test solutions. The solution was added from a dropper until the test strip was just wet. The various test strips were then allowed to dry for 48 hours at room temperature, weighed, and the weight gain recorded in Columns 4, and 6 of the table. 2 /2" x wood strips were cut from cedar shakes, painted with the solution, and allowed to dry for 48 hours. The cloth strips were hung vertically inside a shield. A Bunsen burner with a 1 /2 luminous flame was placed under the lower end of the strip so that the bottom end was into the flame. The cloth was exposed to the flame for 12 seconds and then removed. The time the sample continued to flame and the duration of the afterglow were measured with a stop-watch and recorded respectively in Columns 7 and 8. The tear length was determined by gently lifting a spatula through the charred area until it stopped measuring the length of the tear and recording it in Column 9.

The wood strips were supported at a 45 angle with a split side toward the flame. The 1 /2" luminous flame from a Bunsen burner mounted 1" below and 3" up from the bottom center was allowed to burn for 12 seconds. The time the flame continued to burn (or the time required for the flame to spread to both edges) and the time of the afterglow are recorded. The length and width of the charred area were measured and recorded.

were mixed at 250-265 C. using a Brabender mixer. The mixture was then ground to a powder and test samples were fabricated by molding the powder on a. glass cloth support at 290-300 C. and 1-7 tons per square inch pres sure. Test strips 4 x A x A; inch in size were cut from the molded samples and were burned in a limiting oxygen index test (L.O.I.) (ASTM method D2863-70) as described in Combustion and Flame, 10, 135 (1966). Briefly, this test consists of suspending a sample strip in an upright glass tube of about three inches diameter with air and nitrogen inlets at the bottom to provide a. mixture of known oxygen content, igniting the sample, and deter mining the oxygen concentration at which the sample does not continue to burn. The index is the ratio TABLE 11 Percent B1 in poly- Addltive ester L.0.I.

None 0 o 205 'Iris(2, 3-dihromopropyl) phosphate. 5 0. 262

Product of exmnplo:

1 A mixture of about 75% dlcthyl 3-bromo-2, 2-lflsdnomonthyl)-propylpliospltiate and dlethyl 2, 2-hlsthromomethyl)El-hydroxypropylphos p iona a.

EXAMPLE XIV This example illustrates the resistance to release 01 hydrogen halides by the compounds of the present inven- TABLE Weight; gain After Compound r l Flame glow 'lenr Char o mula 'lotal (pen (pertime time length area Run N0. number) Material treated (name) (percent) rout) cont) (see) (she) (in.) (in, x in.)

1 None Muslin t 2. .do. Commercial viscose 16 10 3 l. "don"... F.R.rayon (l t) H. t 4. do Wood t V V 5, 1M 8) ll ll (l 6 Bil 48 (3,2 (l i) 7 -11) Z6 3. 1 O 0 S 8.5 1.6 (H') ll 0 9 166 70 l3 0 (1 J5 40 7,6 (l (l (35 27 5.2 0 (l 8.5 3. (i 0138 0 0 22 4,4 ll 0 17 3!] 7.8 (l t) 15.. 44 1S 3. 5 (l (l 16 7t 2 .2. (J (l. 58 U (1 1 Fire retardant. rayon containing trls(2,3 dlhromopropyl) phosphate, quantity not. known 1 Consumed in initial 12 seconds.

3 All burned.

4 60 seconds to spread.

5 Sample continued to burn and had to he extinguished.

6 2 3 x 5 on one side, 3% on the. other.

EXAMPLE XllI Molten polyethylene terephthalate and the desired amount of brominated phosphorus compound to give :1

tion. The products of Examples |-5 were subjected to the following tcstt A quantity of five grams of the subject. compound was composition having the percentage of bromine indicated mixed with ml. of water and ml. of (UN NaOH The mixture was stirred for 15 minutes at room temperatu're, then it was acidified by addition of ml. dilute nitric acid. The acidified mixture was titrated with 0.1N AgNO for halide or free halogen using standard Volhard indicator. No titratable halogen was found witth any of the compounds-Similar results are obtained when the same test procedure is applied to the products of Examples 6-10 and to the other compounds of the invention as previously defined.

By procedures such as shown in Examples I-X, phosphates and phosphonates of the defined structures containing chlorine or a mixture of chlorine and bromine are prepared by reacting a suitable phosphate or phosphite with a halogenated alcohol of Formula II where the halogen is chlorine or a mixture of chlorine and bromine. Some of the compounds, particularly the phenyl or alkylphenyl phosphates and phosphonates, are more conveniently prepared by reacting mixtures in the desired proportions of alcohols or alcohol plus the phenol with POCl or P01 as previously explained and as shown in Examples VI to X. For example, by these methods there are obtained compounds such as diethyl 3-chloro-2,2-bis(choromethyl)propylphosphonate,

3-chloro-2,2-bis(hydroxymethyl)propyl diethyl phosphate,

p tert-amylphenyl bis(3-bromo-2,2-bis(chloromethyl) propyl)phosphate, and I 3-bromo-2-(chloromethyD -Z-(hydroxymethyl) propyl diethyl phosphate.

These compounds have similar although somewhat reduced fire-retardant properties as compared to the corresponding brominated compounds.

Other compounds of the invention include and isomers and analogs of these as defined by the general formula.

Although the invention has been described in considerable detail with reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described above and as defined in the appended claims.

We claim: ,1. A compound of the formula R-0 o CHaR wherein n is zero or one; R is lower alkyl; R is R or at least one R" is Br and each remaining R" is at least one R" being OH when n is one.

2. The compound of Claim 1 wherein R is a lower alkyl radical.

3. The compound of Claim 2 of the formula:

OH or Br,

4. The compound of Claim 2 of the formula:

6. The compound of Claim 2 of the formula:

7. The compound of Claim 1 of the formula:

' I" C H BI CHs-CHsO-P OOHr- 43308];

L HgBt 8. The compound of Claim 2 wherein n is zero. 9. The compound of Claim 2 wherein n is one.

References Cited UNITED STATES PATENTS 9,324,205 6/1967 Carpenter et al. 260956 x 3,287,266 11/1966 Southern file a1. 260-965 x 3,456,041 7/1969 Burk etal. 260-967 ANTON H. SU'ITO, Primary Examiner us. 01. xx.

106-45 FP; 117-136; 260-25 AI, 45.7 P, 961, 963, 965 

